Glue solution

ABSTRACT

A glue is disclosed which comprises a solution of at least one water-insoluble synthetic organic polymer, such as PVC or ABS, in a solvent which essentially consists of one or several compounds selected from the group consisting of 5- or 6-membered water-miscible lactones or lactams having a melting point of at the most -10° C., a boiling point of at least 200° C. and a flash point of at least 90° C., such as N-methyl-2-pyrrolidone or γ-butyrolactone. The polymer or polymers may be present in a concentration of between 0.5 and 50% by weight, in particular about 10% by weight. 
     The glue may be used at tropical temperatures without problems arising from solvent vapours and without fire risks. The glue is particularly useful for gluing soft PVC articles to hard PVC articles without loss of the soft character of the soft PVC, and for gluing different polymers, such as PVC on polycarbonate or polycarbonate on polyacrylate.

FIELD OF THE INVENTION

The present invention relates to novel glues for joining articles madefrom water-insoluble synthetic organic polymer materials.

DESCRIPTION OF THE PRIOR ART

The use of polymer materials in e.g. the building industry has had as aconsequence that it is necessary to join, by gluing, prefabricated orfitted articles mainly made from PVC or ABS. Examples of suchcomponenets are roof gutters, roofings, window frames or PVC tubing fortap water or sewage junctions.

The types of glue commonly used so far practically all consist of a10-30% by weight solution of PVC in one or several of the followingsolvents: Butylacetate, cyclohexanone, dimethylformamide ortetrahydrofuran. These solvents all have a relatively low boiling pointand/or flash point and are hazardous to the health when inhaled and, invarying degrees, by skin contact. Thus, official safety demands dictatedby the fire hazards involved and official demands dictated by theoccupational hazards involved are so strict that the compliance to suchdemands renders the use of such solvents costly and in some instancesalmost impossible.

Furthermore, all directions for use of currently available glues demandat the very least a careful de-greasing of the components with ade-greasing agent, normally of the same type as the thinner recommendedfor the glue, thus further subjecting the user to skin contact with asolvent and solvent vapours.

Technically, the low boiling point of most of the currently usedsolvents leads to problems when gluing at elevated temperatures or instrong sunlight, such as the gluing of PVC tubes in subtropical ortropical region where it is common that such gluing operations can onlybe carried out at night.

SUMMARY OF THE INVENTION

The present invention obviates or substantially reduces theabovediscussed disadvantages of the glues according to the prior artboth as regards flammability, occupational hazards and environmentalproblems, and difficulties in connection with gluing at elevatedtemperatures.

The invention relates to a glue comprising a solution of at least onewater-insoluble synthetic organic polymer in a solvent which essentiallyconsists of one or several compounds selected from the group consistingof 5- or 6-membered water-miscible lactones or lactams having a meltingpoint of at the most -10° C., a boiling point of at least 200° C. and aflash point of at least 90° C.

The invention further relates to a method for making a glued jointbetween surfaces of articles made from a material comprisingwater-insoluble synthetic organic polymers, said method comprisingapplying a glue as defined above on at least one of the surfaces to bejoined, joining the surfaces and allowing the joint to develop.

DETAILED DESCRIPTION OF THE INVENTION

Among the lactams, N-alkylated lactams, in particular N-methylatedlactams are preferred, since N-alkylated lactams have lower meltingpoints than N-unsubstituted lactams.

In the present context, the term "alkylated" designates substitutionwith a C₁₋₋₄ alkyl group which may be straight or branched, such asmethyl, ethyl, propyl, isopropyl, butyl and tert.butyl.

Preferred lactones are lactones which are either unsubstituted oralkylated in the 4- or 5-position.

The lactams may be unsubstituted on the ring carbon atoms or alkylatedin the 4- or 5- position.

As examples of 5- or 6-membered water-miscible lactones or lactamshaving a melting point at the most -10° C. and a boiling point of aleast 200° C. may be mentioned N-methyl-2-pyrrolidone (also known asNMP), butyrolactone, N,5-dimethyl-2-pyrrolidone, γ-valerolactone,γ-valerolactone and γ-caprolactone.

A preferred lactam is N-methyl-2-pyrrolidone, and a preferred lactone isγ-butyrolactone. Each of these preferred solvents may be used per se, ora mixture thereof may be used. N-methyl-2-pyrrolidone is especiallypreferred because of its low toxicity (≧7 g/kg in rats).

In the present context, the term "essentially consists of" indicatesthat apart from one or several of the lactones or lactams indicated, thesolvent is preferably free of any substantial amounts of other solvents,but it will be realized that minor amounts of other solvents, evensolvents not fulfilling the criteria set out above, may be added to thesolvents used in the glues according to the invention withoutsubstantially impairing the above-mentioned performance qualities, andsuch admixtures are within the scope of the present invention.

The polymer or polymer mixture dissolved in the solvent to form the glueof the invention may be any water-insoluble synthetic organic polymerwhich is soluble in the lactam or lactone solvent to yield an effectivepolymer glue. As examples of polymers which may be used may be mentionedPVC, ABS, polyacrylate, polycarbonate, cellulose acetate,polyacrylamide, polyamide and polystryrene. Among these, PVC and ABS areespecially important due to their widespread use in articles destinedfor the building, construction and plumbing fields, etc. The polymer orpolymer mixture dissolved in the solvent to form the glue of the presentinvention may be newly made polymer, or it may be polymer waste from theproduction of polymer articles.

As a general rule, the polymer or polymers in a glue is/are preferablyidentical or substantially identical to the polymer or polymers whichare to be joined by means of the glue in question. In other words, thepolymer in a glue for gluing PVC is preferably PVC, the polymer in aglue for gluing ABS is preferably ABS, etc. However, it has also beenfound that two different polymer materials may be glued by means of aglue according to the invention which comprises only one of thepolymers. Thus, both soft and hard PVC may be glued onto polycarbonateby means of a 10% solution of polycarbonate in NMP, and polycarbonatemay be glued onto polyacrylate by means of a 10% solution ofpolycarbonate in NMP.

For use in the various applications the viscosity of the glue may beadjusted within a wide range by increasing or decreasing theconcentration of the polymer or polymers in the glue. The polymer orpolymers are preferably present in the glue according to the inventionin a concentration between 0.5 and 50% by weight, or preferably aconcentration between 2 and 40% by weight, usually between 3 and 30% byweight. For most practical applications, a suitable glue will containthe polymer or polymers in a concentration of between 5 and 20%, inparticular 8 and 16% such as about 10%, by weight.

If desired, a thixotropic agent such as colloidal silica may beincorporated in the glue according to the present invention in order toavoid dripping of the glue without resorting to an otherwise undesiredhigh concentration of the polymer or polymers. The colloidal silica may,for example, be of the type sold under the trademarks "Aerosil®" (fromDegussa, BRD) or "HDK" (from Wacker Chemie, BRD) and may be incorporatedin any suitable amounts such as from about 0.1 to about 3% by weight.Also, a viscosity-adjusting agent may be incorporated, such as baryte ina concentration of from 1 to 10% by weight, adi-2ethylhexylamine-neutralized carboxyvinyl polymer (such as "Carbopol"934 from Goodrich Chemicals) in a concentration of from about 0.5 toabout 1% by weight, or a hydroxyethyl cellulose (such as "Cellosize" QP100M from Union Carbide) in a concentration of from about 0.5 to about2% by weight.

One of the advantages of the glue according to the invention is that itpermits the gluing of components which were not, in the prior art,easily gluable by means of the known compositions.

As examples of such systems which are now easily gluable may bementioned gluing of soft or softened PVC to hard PVC where prior artglues based on conventional solvents often failed, probably due toundesired interaction with the plasticizers in the soft PVC. Accordingto the invention this permits e.g. the easy gluing of soft PVC hoses tohard PVC fittings in connection with the installation of e.g. swimmingpools, or in connection with the construction of laboratory apparatus(gluing of soft PVC hoses to hard PVC tubes, in dishwashers, washingmachines, etc.).

A further possibility is the gluing or repair of soft PVC articles wherea glue according to the invention may be constructed with a sufficientbody and viscosity to fill cracks or fissures and other irregularitiesand join them to attain the original dense structure, with retention ofthe general soft character of the original article. This is ascribableto the characteristics of the glue of the invention to the effect thatit does not interfere with or extract plasticizer from the PVC, incontrast to conventional glues, the solvents of which are also much moreefficient solvents of the plasticizer.

In a textbook on NMP (cf. "NMP, N-methyl-2-pyrrolidone Handbook", GAFCorporation, N.Y. 1972, page 47), it is mentioned that NMP may improveperformance in such applications as rubber and vinyl cements, and it isalso suggested to use NMP as a solvent welding agent. The textbook,however, does not state or indicate that NMP may be used as the sole orsubstantially the sole solvent in glues, and the mention of NMP as asolvent welding agent does not anticipate the use of NMP as a gluesolvent. The technology of gluing is distinct from welding of plasticsin many regards: Firstly, gluing does not solely depend upon dissolutionof the plastic parts to be joined. Secondly, gluing will serve to fillvoids between the articles to be joined because of the body constitutedby the solid contents of the glue itself. Thirdly, solvent weldingcannot be used in practice in several applications beacuse the solventwould tend to drip or spread over a too large area. Fourthly, solventwelding would tend to apply too much solvent at the junction with theresult that the polymer material adjacent to the joint would soften to atoo high degree and it would take a too long period before the fullstrength had been developed through migration of the solvent.

The invention is illustrated in the following non-limiting examples.

EXAMPLE 1 Preparation of an NMP-based glue containing PVC

In a closed vessel 10% by weight of PVC-granulate (trademark Vinnol®from Wacker Chemie, BRD) are added to NMP at room temperature undervigorous stirring until a homogeneous solution is obtained.

EXAMPLE 2 Preparation of an NMP-based glue containing PVC-waste

In a closed vessel 10% by weight of PVC granulate (made from waste fromthe production of hard PVC articles) are added to NMP under vigorousstirring at room temperature until a homogeneous solution is obtained.

EXAMPLE 3 Preparation of an NMP-based glue containing ABS

By following the procedure described in Examples 1 and 2, butsubstituting ABS granulate for PVC granulate, a solution of 10% byweight of ABS in NMP is prepared.

EXAMPLE 4 Preparation of an NMP-based glue containing PVC and ABS

By following the procedure described in Examples 1 and 2 a solution of 5parts by weight of PVC granulate and 5 parts by weight of ABS granulatein 90 parts by weight of NMP is prepared.

EXAMPLE 5 Pressure testing of glued joints

From a length of PVC-tube with a nominal diameter of about 50 mm werecut two pieces with a length of about 50 cm. To each of the four ends ofthe two pieces of tubing were glued a closed tube sleeve with an insidediameter of about 50.5 mm. One of the sleeves of each length of tube wasfitted with a pressure coupling and a manometer. The gluing wasperformed by means of a 10% by weight solution of PVC inN-methyl-2-pyrrolidone prepared as described in Example 1. The gluingwas performed by applying a thin layer of glue to the outside surface ofthe tube end about 3 cm up the length of the tube, fitting the sleeveover the end of the tube, rotating the sleeve on the tube end todistribute the glue and leaving the joints to set.

Tube No. 1 had a diameter at one end of between 50.0 mm and 50.2 mm andat the other end of between 50.0 mm and 50.2 mm, which ends were fittedwith closed sleeves with an inside diameter of 50.5 mm and 50.4 mm,respectively, thus providing joints with a gap between the surfaces of0.3-0.5 mm and 0.2-0.4 mm, respectively. After the glue had been appliedand the sleeves fitted, the glue was allowed to set for 4 hours at roomtemperature. Thereafter, the gluing was pressure tested at 10 kg/cm²water pressure for 15 minutes and thereafter at 19-20 kg/cm² waterpressure for 15 minutes. No leaks were observed.

Tube No. 2 had end diameters of 49.9-50.3 mm and 49.9-50.3 mm, and theends were fitted with closed sleeves with inside measures of 50.5 mm and50.3-50.5 mm, respectively, thus producing joints with a gap between thesurfaces of 0.2-0.6 mm and 0.2-0.6 mm, respectively. The sleeves wereglued to the tube in the same manner as above, and the glue was allowedto set for 4 hours at room temperature. Pressure testing was performedat 8 kg/cm² water pressure for 15 minutes followed by 19-20 kg/cm² waterpressure for 15 minutes. No leaks were observed.

EXAMPLE 6 Gluing of soft PVC onto hard PVC

To the outside surface of the end of a piece of hard PVC tube (outsidediameter 16 mm) a glue prepared according to Example 1 was applied ca. 1cm up the length of the tube. A piece of soft PVC hose (inside diameter13 mm) was thereafter fitted over the end of the tube and rotatedslightly to distribute the glue, whereafter the glue was allowed to set.The gluing showed no cracking or brittling of the hose, and it was notpossible to pull the hose off.

I claim:
 1. A method for making a glued joint between surfaces ofarticles made from a material comprising water-insoluble syntheticorganic polymers, said method comprising applying a glue solution whichconsists essentially of a solvent of at least one 5- or 6-memberedwater-miscible lactone or lactam having a melting point not greater than-10° C., a boiling point of at least 200° C. and a flash point of atleast 90° C., and at least one water-insoluble synthetic or naturalorganic polymer dissolved therein, on at least one of the surfaces to bejoined; joining said surfaces; and allowing a joint to develop.
 2. Themethod as claim in claim 1 wherein the lactams are N-alkylated.
 3. Themethod as claimed in claim 2, wherein the N-alkylated lactam is anN-methylated lactam.
 4. The method as claimed in claim 1, wherein thelactones are unsubstituted or alkylated in the 4- or 5-position.
 5. Themethod as claimed in claim 2, wherein the lactams are unsubstituted onthe ring carbons or alkylated in the 4- or 5-position.
 6. The method asclaimed in claim 2, wherein the solvent consists of a mixture ofN-methyl-2-pyrrolidone and γ-butyrolactone.
 7. The method as claimed inclaim 1, wherein the solvent consists of N-methyl-2-pyrrolidone.
 8. Themethod as claimed in claim 1, wherein the solvent consists ofγ-butyrolactone.
 9. The method as claimed in claim 1, wherein thepolymer is at least one member selected from the group consisting ofPVC, ABS, polyacrylate, polycarbonate, cellulose acetate,polyacrylamide, polyamide and polystyrene.
 10. The method as claimed inclaim 9, wherein the polymer is PVC.
 11. The method as claimed in claim9, wherein the polymer is ABS.
 12. The method as claimed in claim 9,wherein the polymer is a mixture of PVC and ABS.
 13. The method asclaimed in claim 9, wherein the polymer or polymers is/are present in aconcentration of between 0.1 and 50% by weight.
 14. The method asclaimed in claim 13, wherein the polymer or polymers is/are present in aconcentration of between 3 and 30% by weight.
 15. The method as claimedin claim 14, wherein the polymer or polymer is/are present in aconcentration of between 5 and 20% by weight.
 16. The method as claimedin claim 15, wherein the polymer or polymers is/are present in aconcentration of between 8 and 16% by weight.
 17. The method as claimedin claim 16, wherein the polymer or polymer is/are present in aconcentration of about 10% by weight.
 18. The method as claimed in claim1, wherein the glue solution consists essentially ofN-methyl-2-pyrrolidone solvent and PVC dissolved therein.
 19. The methodas claimed in claim 18, wherein the ariticle is made of PVC.
 20. Themethod as claimed in claim 1, wherein the glue solution further containsa thixotropic agent.
 21. The method as claimed in claim 20, wherein thethixotropic agent is colloidal silica.
 22. The method as claimed inclaim 1, wherein the glue solution further contains aviscosity-adjusting agent.
 23. A glue solution which consistsessentially of γ-butyrolactone and at least one water-insolublesynthetic or natural organic polymer dissolved therein.
 24. A gluesolution which consists essentially of a solvent of at least one 5- or6-membered water-miscible lactone or lactam having a melting point notgreater than -10° C., a boiling point of at least 200° C. and a flashpoint of at least 90° C.; and a polymer selected from the groupconsisting of polyacrylate, polyacrylamide, polyamide, polystyrene,cellulose acetate, ABS or a mixture of ABS and PVC dissolved therein.